A vehicle side-on collision occupant protection device described in Patent Document 1 (Japanese Patent Application Laid-Open (JP-A) No. 2008-080988) includes a side airbag module installed inside a side support of a seatback at the vehicle width direction outer side of a seat side frame, and a bracket (side reaction force plate) fixed at the seat side frame. The bracket includes an extension portion extending in the vehicle front-rear direction at the vehicle width direction outer side of the side airbag module. A vehicle front side end portion of the extension portion extends as far as the vicinity of a front end edge portion (frame portion) of the side support, and the side airbag is supported from the door side during initial deployment of the side airbag. This enables the occupant restraining force of the side airbag to be increased at an early stage.
Patent Document 2 (JP-A No. H09-286298) and Patent Document 3 (JP-A No. 2008-087631) below are examples of related art publications relevant to the invention of the present invention.